Navigational travel time computer

ABSTRACT

A computer scale member has a wind or current triangle scale based on a standard navigational scale on one edge thereof. The member also has a plurality of travel time scales based on travel time at predetermined speeds. At one end of the member is a hole and a compass index around the hole. A clamping device releasably clamps the member to a clamping section on the free end of a lost motion arm mechanism, the other end of which is attached to a map supporting surface.

United States Patent Marshall [54] N AVIGATIONAL TRAVEL TIME COMPUTER[72] inventor: John Marshall, 1228 N. Quantico St., Arlington, Va. 22205[22] Filed:

1151 3,683,506 [4 1 Aug. 15, 1972 FOREIGN PATENTS QR APPLICATIONS565,953 12/1944 Great Britain ..33/79 A Primary Examiner-Harry N.Haroian Attorney-Wenderoth, Lind & Ponack ABSTRACT A computer scalemember has a wind or current triangle scale based on a standardnavigational scale on one edge thereof. The member also has a pluralityof travel time scales based on travel time at predetermined speeds. Atone end of the member is a hole and a compass index around the hole. Aclamping device releasablyclamps the member to a clamping section on thefree end of a lost motion arm mechanism, the

other end of which is attached to a map supporting surface.

l5Claims,5DrawingFigures Patented Aug. 15, 1972 3,683,506

4 Sheets-Sheet 1 INVENTOR JOHN MARSHALL BY fixed! ATTORNEYS INVENTORJOHN MARSHALL ATTORNEYS Patented Aug. 15,1972

4 Sheets-Sheet 2 NQE mm mm Om q ma mm om mm om Q 9 m o Patented Aug. 15,1972 3,683,506

4 Sheets-Sheet s L V w. M MW. .4 INVENTOR JOHN MARSHALL ATTORNEYSNAVIGATIONAL TRAVEL TIME COMPUTER BACKGROUND OF THE INVENTION Thepresent invention relates to a travel time computer for use in aerialand nautical navigation.

More particularly, the present invention relates to such a device by theuse of which the effects of wind or currents may-be readily computed andthe estimated travel time may be simply determined.

Even more particularly, the present invention relates to such a deviceby the use of which the estimated travel time might be checked duringtravel.

Yet more particularly, the present invention relates to such a devicewhich is portable and extremely simple to use.

An important determination to be made in aerial and nautical navigationis the estimated time of travel. It is not possible to make thisdetermination by merely considering the distance and fixed speed of thecraft. This is due to the effects of wind currents. For instance, a headwind will slow a craft down, and a tail wind will speed a craft up.Similarly, a side wind would veer the aircraft off course. Thus, in thecase of a head wind or tail wind, the effective travel time (the groundspeed of the aircraft) would be less or greater, respectively than thatcomputed. In the case of a side wind, the aircraft would never reach thedestination, but would rather pass by the destination on either side.Water currents have similar effects on water craft.

A great many systems have been developed to account for the effects ofwind and currents to enable an operator of an aircraft or watercraft toaccurately estimate travel time. However, none of these systems havebeen entirely successful for numerous reasons. These prior systems haverequired numerous manipulations and calculations to determine estimatedtravel time. Particularly in the case of a small aircraft or watercraft,the operator does not have time to check these calculations duringtravel. Due to this complexity operators in many cases just simply nevermake the calculations and rely upon noticing landmarks and theirjudgement to determine the proper course and estimate the length oftravel time. However, the disadvantages and dangers of such practice aremanifest. A mistake in judgement or an error in recognizing a landmarkmay result in the operator becoming hopelessly lost.

With this background in mind, it is a primary object of the presentinvention to provide a travel time computer for use in either aerial ornautical navigation which may very easily be used to determine estimatedtravel time.

It is a further object of the present invention to provide such a devicewhich may be easily used during travel to check on the estimated traveltime.

It is a yet further object of the present invention to provide such adevice which is portable and compact and very simple to use.

It is still a further object of the present invention to provide asimplified modification for use in determining and checking on theestimated travel time.

These objects are achieved in accordance with the present invention bythe provision of a novel computer which is made portable and compact. Aportable clipboard is provided with a lost motion arm mechanism thereon.Movably mounted on the end of the lost motion arm mechanism is a novelcomputer scale member.

At the end of the computer scale member which is movable mounted on thelost motion arm mechanism is a double compass bearing index for use inplotting a wind or current triangle. On one edge of the computer scalemember is a novel wind triangle scale which is miniaturized and basedupon some standard scale such as the Sectional Aeronautical Chart scale.Also on the computer scale member are a series of travel time scalesbased upon increments of ground speed and having indicia in travel time.Conveniently, all of the above scales and indexes appear on both sidesof the novel computer scale member. In a simplified modification of thepresent invention, a computer including only the travel time scales isprovided.

Other objects and features of the invention will be made clear by thefollowing description taken together with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevational view of apreferred embodiment of the present invention;

FIG. 2 is an enlarged plan view of the computer scale shown in FIG. 1;

FIG. 3 is a cross-sectional view taken along line III- III in FIG. 1;

FIG. 4 is a plan view of a navigational chart showing wind triangle andestimated travel time computations using the device of FIG. 1; and

FIG. 5 is a plan view of a simplified modification of the estimatedtravel time computer in accordance with the present invention.

with reference now to the drawings, the novel travel time computer willbe described in detail. In FIG. 1 the computer is generally indicated bythe reference numeral l and includes a portable clipboard having abacking plate 2 and a cover plate 3. Cover plate 3 is attached to andadapted to be folded over backing plate 2 by any suitable means such ascreased portion 4. On one edge of backing plate 2 is mounted a lostmotion arm mechanism 5 by a suitable bracket 6. Bracket 6 has a raisedlevel 7 at the connection of the lost motion arm mechanism 5 such thatthe mechanism 5 is slightly raised above the surface of the backingplate 2. The principle of operation of a lost motion arm mechanism iswell known. Therefore, a detailed description of this mechanism will bedispensed with herein. However, the purpose of the lost motion armmechanism is to move a straight edge anywhere over a surface whilealways maintaining the edge parallel to its original position.

The lost motion arm mechanism 5 is connected at the free end thereofwith a computer scale member bracket 8. The computer scale memberbracket 8 has a raised portion 9 at the area of connection with the lostmotion arm mechanism 5 to insure that the mechanism 5 is slightly raisedabove the surface of the backing plate 2. The computer scale memberbracket 8 has a generally circular clamping section 10. A hole 11 iscentrally located within the clamping section 10. Around the upper outerperiphery of clamping section 10 is positioned a marking surface 12, thepurpose of which will be described in more detail below.

A computer scale member 13 having a centrally located hole 14 on one endthereof is adapted to be clamped to clamping section 10. As shown inFIG. 3, a threaded clamping bolt 15 having a supporting flange l6thereon is inserted through holes 14 and 11. A nut 17 screws on to bolt15 to hold clamping flange and computer scale member 13 in placetogether. As will be apparent from FIG. 3, computer scale member 13 ismovably mounted upon the loosening of nut 17.

A suitably scaled aerial or nautical map 18 is adapted to be positionedon backing plate 2 by any desirable or suitable clamping arrangement. Ithas been found that a particularly effective and convenient arrangementmay be provided by large clips such as illustrated by reference numerals19 in FIG. 1. Cover plate 3 has a suitably located opening 20 thereinwhich is adapted to receive nut 17 when the cover plate 3 is folded overbacking plate 2. Thus, it will be seen that the assembly illustrated inFIG. 1 provides a compact and portable navigational computer.

With reference now to FIG. 2 of the drawings, the computer scale member13 will be described in more detail. Computer scale member 13 isgenerally in the form of a rectangle. As previously mentioned, anopening 14 is centrally located in one end of the scale for attachmentto clamping section 10 of the lost motion arm mechanism 5. If desiredthe end of the scale member may be rounded as at 21. A double compassindex 22 is provided annularly around opening 14 in such a manner thatit is visible around clamping flange 10 when the computer scale member13 is clamped thereto. A single compass index may be provided ratherthan a double compass index. However, it will be manifest that theprovision of a double compass index provides for more convenience ofoperation of the computer device.

A wind or current .triangle scale 23 is provided on one longitudinaledge of computer scale member 13. Triangle scale 23 is convenientlyminiaturized and conveniently based on some other standard scale. In theembodiment shown in FIG. 2, wind triangle scale 23 is based on theSectional Aeronautical Chart scale (statute or sectional scale).Further, in the embodiment shown in FIG. 2, wind triangle scale 23 isminiaturized such that one increment thereof is one-fourth the size ofthe same increment on the Sectional scale. Suitable indicia 24, 25,26and 27 are provided in close relationship to wind triangle scale 23 foruse in a manner to be described in more detail below. On the oppositelongitudinal edge of computer scale member 13 may be convenientlyprovided a Sectional Aeronautical Chart scale 28.

Between wind triangle scale 23 and Sectional Aeronautical Chart scale 28are provided a plurality of travel time scales 29-38. Scales 29-38 arebased upon various ground speeds (in the case of aerial navigation, oreffective speeds in the case of nautical navigation) such as 80 mph, 90mph, 100 mph....170 mph. These values are indicated on the right handends of the scales as viewed in FIG. 2. The indicia on each of thescales 29-38 are increments such as minutes of travel time. Forinstance, in scale 29, the increment indicated by 5 represents 5 minutesof travel time at a ground speed of 80 mph. As will be apparent, thelengths on the scales of the increments of time become increasinglylonger as the ground speeds increase.

Conveniently, slots 39 may be provided between pairs of the travel timescales to facilitate marking and computation with regard thereto.Alternatively, holes could be provided at each end of scales 29-38 tofacilitate marking.

In a preferred embodiment of the present invention the computer scalemember 13 consists of a clear flexible plastic material with the variousindicia and scales printed thereon in a suitable manner. However, it isto be understood that the computer scale member 13 may be made of anysuitable or desirable material, such as aluminum, steel, fiberboard etc.

Furthermore, it is to be understood that it is within the contemplationof the scope of the present invention that the reverse side (not shown)of computer scale member 13 contains additional incremental travel timescales. For instance, the reverse side of computer scale member 13 shownin FIG. 2 could contain additional travel time scales based on groundspeeds of from mph to 270 mph. The reverse side of the computer scalemember 13 would also contain a duplicate compass index 22, wind trianglescale 23, indicia 24-37, and Sectional Aeronautical Chart scale 28.

Although the above-described preferred embodiment of the presentinvention has shown 10 travel time scales on each side of the computerscale member 13, it is to be understood that it is considered to bewithin the scope of the present invention to provide a greater or lessernumber of such scales. It is to be further understood that although inthe preferred embodiment the travel time scales have been computed inground speed increments of 10 mph, it is contemplated that otherincrements can be used. For instance, if the aircraft or watercraft isrelatively slow, it may be desirable to use smaller increments. However,if the craft is relatively fast, it may be desirable to use relativelylarger increments.

With reference now to FIG. 4 of the drawings, the computations possiblewith the device shown in FIG. 1 will be described. For purposes ofclarity, the various positions of the computer itself, have beeneliminated from FIG. 4.

A suitable map such as map 18 is positioned on the backing plate 2 bymeans such as clamps l9. Assume that the operator of the craft wishes totravel from point A to point B, for instance two airports. A line 40,which represents the actual course of travel, is drawn between points Aand B. Nut 17 is loosened, such that computer scale member 13 ismovable. One edge of the scale is then aligned with a convenient compassrose or meridian 41 on the map. The nut 17 is then tightened so thatcomputer scale member 13 is rigidly secured. Marking surface 12 ismarked at North as indicated on compass index 22. Alternatively, markingsurface 12 may be replaced by a movable pointer which may be mounted formovement around the periphery of clamping section 10.

Assume that the wind speed information available indicates that the windis 30 mph (statute miles) from the northeast. Since northeast represent45 on the compass, nut I7 is loosened and computer scale member 13 isturned until 45 on the compass scale 22 is aligned with the previouslymade mark on marking surface 12. Nut 17 is then clamped such thatcomputer scale member 13 is secure. The zero point on the wind trianglescale 23 is then aligned anywhere along course line 40. Since the windis indicated as 30 mph a wind vector of 30 on the wind triangle scale 23is drawn in the direction of the name of the wind, i.e. northeast. Windvector 42 represents the effect of the wind upon the course of thecraft.

Next assume that the given air speed of the aircraft is 135 mph. The nut17 is loosened and the wind triangle scale 23 is positioned such thatthe zero point thereof intersects course line 40 in the generaldirection of starting point A and the 135 point intersects the end ofwind vector 42 or vice versa. These points are indicated as C and D,respectively, in FIG. 4. The vector CE represents both the flying timein minutes and the effective ground speed along course line 40. This istrue since the wind triangle scale 23 has been miniaturized to onequarter of the Sectional Aeronautical Chart scale (statute miles). Thus,for convenience, computations based on the wind triangle scale 23 areone quarter the size of computations which would be based on statutemiles. Also, time computations are accordingly based on miles perquarter hour (15 minutes). It is to be understood, however, that thewind triangle scale could be based upon any other fraction of, or couldbe the same as the Sectional Aeronautical Chart or any other suitablechart.

If it is desired to know the ground speed of the craft, this may bereadily determined by measuring vector CE along the wind triangle scale.When this is done, it is found that the ground speed is approximately120 mph. This can be verified by measuring vector CE on the 120 mphtravel time scale. When this is done, it is found that the length intime of vector CE corresponds approximately to 15 minutes.Altematively,.the ground speed might be determined merely by quicklycomparing the length of vector CE with the various travel time scalesand aligning the vector with the scale which most nearly aligns with 15minutes.

Once the proper travel time scale has been determined, it will bereadily apparent that the total estimated travel time between points Aand B may be readily determined. This is done by measuring course line40 along the determined travel time scale and reading the estimatedtravel time in minutes. When this is done with regard to the abovedescribed example, using the 120 mph travel time scale, it will be foundthat it will take approximately 37 minutes to travel from point A topoint B.

The purpose of indicia 2427 of FIG. 2 will now be more apparent from theabove discussion. Indicia 24 states that when using the scales describedwith wind and air speed information in terms of statute miles, themeasurement of vector CE will be 15 minutes of travel time. Indicia 25indicates that the same vector will indicate 13 minutes of travel timeif wind and air speed information are in nautical miles. lndicia 26indicates that vector CE will measure 24 minutes of travel time when theair speed and wind information are in kilometers. lndicia 27 merelyindicates that the indicia 24 through 26 should be doubled when the mapis to the WAC scale (World Aeronautical Chart). Since the statute milesscale and the WAC scale are the two most commonly used, indicia 24-27should cover most common uses. However, it is to be understood that thescope of the present invention contemplates the use of other scale maps.For instance, in nautical navigation, a great many varying scaled mapsare available.

It is also to be understood that the assembly of FIG. 1 can be used forother common navigational purposes. For instance, it will be apparentthat nut 17 may be tightened when one edge of computer scale member 13is aligned with vector CD, and the compass index may be read at thepoint which was previously marked on marking surface 12. This compassreading will indicate the bearing or direction which the craft should beheaded to travel over course line 40.

The computer scale member 13 may also be used during travel to check onthe estimated travel time. For instance, the operator travelling alongcourse 40 knows that he will pass closely by a particular landmark F.This landmark might be any easily recognized fixture such as a bridge, aradio tower, a water tower, etc. The operator need only record thetravel time between starting point A and check point F or between anytwo points. If this travel time is for instance 10 minutes, the operatorneed merely compare the various travel time scales to find the one inwhich a travel time of 10 minutes aligns between points A and F alongcourse line 40. In the above example, this travel time scale is the mphscale. Thus, the operator has determined his ground speed as 110 mph.The operator may then use this scale to measure the travel time betweenstarting point A and destination point B. When this is done, theoperator will determine that his estimated flight time between points Aand B will be approximately 40 minutes. If the operator had made apreflight estimation as previously discussed and determined that hisestimated travel time would be 37 minutes, he now realizes that he isflying into a stronger wind. This results in a lower ground speed and alonger travel time. 2

The device of the present invention may also be used by an operatorduring travel to correct for an incorrect bearing due to, for instance,incorrect wind information. For instance, the operator intending to flyover course line 40 might discover after a given period of time, such as17 minutes, that he is in fact flying over a recognizable landmark G. Hethen knows that his actual course line is along AG. The operator thencompares line AG with travel time scales 29-38 to determine whichcorresponds to a travel time of 17 minutes. In the above example, thisis the mph scale. A vector AH, corresponding to 15 minutes on the 120mph scale is then marked off along line AG. The operator then draws acourse bearing line through point A which is parallel to vector CD.Along this bearing line is marked a vector AJ representing an airspeedof mph. Vector HJ then represents the actual wind vector encountered.The length of wind vector HJ may be measured along wind triangle scale23. When this is done, it is found that the wind has a velocity ofapproximately 63 mph. The direction of the wind may be measured from thecompass index. This wind information may then be used as previouslydescribed to recalculate a wind triangle and to determine estimatedtravel time between points G and B. Thus, it will be seen that by theprovision of applicants novel device flight corrections may be veryreadily made during travel.

The device of the present invention may also be used during travel fornavigational calculations necessitated by a change in destination. Forinstance, when the operator has reached point K along course line 40, it

may for one reason or another be necessary to change his destination,for instance to airport L. Using the previously available windinformation, wind vector LM is plotted. Since the air speed remains 135mph, wind triangle scale 23 is placed such that the 135 point intersectsthe end of wind vector LM, and the zero point intersects course line KL.Vector NL then represents minutes of flying time. When vector NL ismeasured along wind triangle scale 23, it is found that the ground speedis 105 mph. Since the device illustrated has no 105 mph travel timescale vector KL is measured along both the 100 mph and the 110 mphtravel time scales. When this is done, it is found that vector KLmeasures 21 minutes on the former and 19 minutes on the latter.Therefore the estimated travel time between points K and L will beapproximately 20 minutes.

Thus, it will be apparent that changes in course during travel mayeasily be accommodated and plotted with the device of the presentinvention.

It will be even further apparent to those skilled in the art that agreat many other and additional navigational calculations may be made bythe employment of applicants computer device.

With reference now to FIG. 5 of the drawings, a simplified embodiment ofthe computer device of the present invention will be described. Acomputer scale member 50 includes a plurality of travel time scales51-60 on one side thereof. In the example shown, scales 51-60 correspondto scales 29-38 of the embodiment shown in FIG. 2. That is, the scales51-60 are based upon ground speeds of 80 mph, 90 mph, 170 mph. A reverseside of computer scale member 50 may likewise have further travel timescales. For instance, the reverse side of computer scale member 50 mighthave travel time scales based on ground speeds of from 180 mph to 270mph. It will be noted that the length of travel time scales on computerscale member 50 are longer than the lengths of travel time scales 29-38on computer scale member 13 shown in FIG. 2. However, it is to beunderstood that the lengths of the travel time scales on both computerscale members 50 and 13 may be made longer or shorter, depending uponconvenience and space considerations. Computer scale member 50 mayconveniently have holes or slots 61 between the travel time scale. Theslots 61 are similar to the slots 39 on computer scale member and allowaccess of a pencil or other instrument with regard to each of the traveltime scales. In the preferred embodiment, computer scale member 50 ismade of a clear, flexible plastic material, and the various scales andindica are printed thereon. However, it is to be understood thatcomputer scale member 50 may be made of any suitable or desirablematerial such as aluminum, stainless steel, etc.

Computer scale member 50 is used to check on travel time in the samemanner as discussed above with regard to scale member 13.

In the above examples, the present invention has been discussed withregard to aerial navigation. However, it is to be understood that thedevice is equally applicable to nautical navigation. The speed of theboat would of course be sustituted for air speed. Additionally, tide andwater current information would be substituted for wind information.Also, the increments of the travel time scales would be much smaller.

It will be apparent that a greatly simplified navigational computer hasbeen provided. The device has application both in aerial and nauticalnavigation. The device is compact and portable and is thus suitable fora small aircraft or watercraft. In addition, the device is extremelysimple to use and operate. This is of great importance in an aircraft orwatercraft operated by only one person. The operator need devote only avery few brief moments during travel to check on estimated travel time.In addition, such operators will be encouraged to use the device of thepresent invention in pretravel calculations due to its simple nature andlack of complexity.

Although preferred embodiments of the invention have been described indetail, such description is intended to be illustrative only and notrestrictive, since many details of the construction of the invention maybe altered or modified without departing from the spirit or scopethereof.

What is claimed is:

1. A navigational computer comprising a mounting surface adapted to havea map positioned thereon; a computer scale member; and means formounting said computer scale member for movement over said map; saidcomputer scale member having a wind or current triangle scale thereon,said wind or current triangle scale including indicia having apredetermined relationship to a standard navigational chart scale, and aplurality of travel time scales thereon, each of said travel time scaleshaving indicia representing time of travel at a different predeterminedspeed, said wind or current triangle scale and said travel time scalesbeing dimensioned such that an increment on said wind or currenttriangle scale corresponds to a predetermined length of time on saidtravel time scale corresponding to said increment on said wind orcurrent triangle scale.

2. A navigational computer as claimed in claim 1, further comprising aportable clipboard having a backing plate and a cover plate attached tosaid backing plate, said mounting surface being said backing plate, andmeans for selectively folding said cover plate over said backing plate.

3. A navigational computer as claimed in claim 2, wherein said mountingmeans comprises a lost motion arm mechanism, a bracket mounting saidlost motion arm mechanism on said backing plate, and a computer scalemember bracket releasably attached to said computer scale member, saidbracket and said computer scale member bracket each having raised levelsthereon to raise said lost motion arm mechanism above said map.

4. A navigational computer as claimed in claim 3, wherein said computerscale member has a central hole through one end thereof, and saidcomputer scale member bracket comprises a generally circular clampingsection having a central bore therethrough, a bolt adapted to extendthrough said bore and said hole, and a nut adapted to selectively clampsaid computer scale member to said clamping section.

5. A navigational computer as claimed in claim 4, further comprising amarking surface adjacent the periphery of said clamping section and acompass index annularly located around said hole, whereby said index isvisible when said computer scale member is clamped to said clampingsection.

6. A navigational computer as claimed in claim 5, wherein said compassindex is a double index.

7. A navigational computer as claimed in claim 4, further comprising amovable pointer mounted for movement around the periphery of saidclamping section and a compass index annularly located around said hole,whereby said index is visible when said computer scale member is clampedto said clamping section.

8. A navigational computer as claimed in claim 7, wherein said compassindex is a double index.

9. A navigational computer as claimed in claim 1, wherein said standardnavigational chart scale is the Sectional Aeronautical Chart scale.

10. A navigational computer as claimed in claim 7, wherein saidpredetermined relationship is such that the length of an increment ofsaid wind triangle scale equals one-fourth the length of such incrementon said Sectional Aeronautical Chart scale.

11. A navigational computer as claimed in claim 1, wherein saidpredetermined speeds are gound speeds.

12. A navigational computer as claimed in claim 1, further comprising aplurality of slots through said computer scale member between pairs ofsaid travel time scales.

13. A navigational computer as claimed in claim 1, further comprising aplurality of holes through said computer scale member at the ends ofsaid travel time scales.

14. A navigational computer as claimed in claim 1, further comprising asecond plurality of travel time scales on the side of said computerscale member opposite said plurality of travel time scales.

15. A navigational computer as claimed in claim 1, wherein said computerscale member consists of a clear, flexible plastic material.

1. A navigational computer comprising a mounting surface adapted to havea map positioned thereon; a computer scale member; and means formounting said computer scale member for movement over said map; saidcomputer scale member having a wind or current triangle scale thereon,said wind or current triangle scale including indicia having apredetermined relationship to a standard navigational chart scale, and aplurality of travel time scales thereon, each of said travel time scaleshaving indicia representing time of travel at a different predeterminedspeed, said wind or current triangle scale and said travel time scalesbeing dimensioned such that an increment on said wind or currenttriangle scale corresponds to a predetermined length of time on saidtravel time scale corresponding to said increment on said wind orcurrent triangle scale.
 2. A navigational computer as claimed in claim1, further comprising a portable clipboard having a backing plate and acover plate attached to said backing plate, said mounting surface beingsaid backing plate, and means for selectively folding said cover plateover said backing plate.
 3. A navigational computer as claimed in claim2, wherein said mounting means comprises a lost motion arm mechanism, abracket mounting said lost motion arm mechanism on said backing plate,and a computer scale member bracket releasably attached to said computerscale member, said bracket and said computer scale member bracket eachhaving raised levels thereon to raise said lost motion arm mechanismabove said map.
 4. A navigational computer as claimed in claim 3,wherein said computer scale member has a central hole through one endthereof, and said computer scale member bracket comprises a generallycircular clamping section having a central bore therethrough, a boltadapted to extend through said bore and said hole, and a nut adapted toselectively clamp said computer scale member to said clamping section.5. A navigational computer as claimed in claim 4, further comprising amarking surface adjacent the periphery of said clamping section and acompass index annularly located around said hole, whereby sAid index isvisible when said computer scale member is clamped to said clampingsection.
 6. A navigational computer as claimed in claim 5, wherein saidcompass index is a double index.
 7. A navigational computer as claimedin claim 4, further comprising a movable pointer mounted for movementaround the periphery of said clamping section and a compass indexannularly located around said hole, whereby said index is visible whensaid computer scale member is clamped to said clamping section.
 8. Anavigational computer as claimed in claim 7, wherein said compass indexis a double index.
 9. A navigational computer as claimed in claim 1,wherein said standard navigational chart scale is the SectionalAeronautical Chart scale.
 10. A navigational computer as claimed inclaim 7, wherein said predetermined relationship is such that the lengthof an increment of said wind triangle scale equals one-fourth the lengthof such increment on said Sectional Aeronautical Chart scale.
 11. Anavigational computer as claimed in claim 1, wherein said predeterminedspeeds are gound speeds.
 12. A navigational computer as claimed in claim1, further comprising a plurality of slots through said computer scalemember between pairs of said travel time scales.
 13. A navigationalcomputer as claimed in claim 1, further comprising a plurality of holesthrough said computer scale member at the ends of said travel timescales.
 14. A navigational computer as claimed in claim 1, furthercomprising a second plurality of travel time scales on the side of saidcomputer scale member opposite said plurality of travel time scales. 15.A navigational computer as claimed in claim 1, wherein said computerscale member consists of a clear, flexible plastic material.